1. Field of the Invention
The present invention relates to a pressure switch wherein a moving contact piece provided in a switch mechanism swings to engage and disengage the corresponding fixed contact for switching operation following the travel of a member moving in response to pressure applied (hereinafter referred to as a pressure-moved member).
2. Brief Description of the Prior Art
Pressure switches of the type available heretofore have been such that a moving contact piece provided in a switch mechnism was made of a conductive elastic piece, e.g. a leaf, spring or the like and the one end of said moving contact piece was secured and supported nonelastically to work as a swinging fulcrum.
However, these conventional pressure switches have incurred the following inconveniences.
Namely, the moving contact piece has swung and reset automatically with the self-retaining elasticity pivoting on the aforementioned one end thereof. However, the self-retaining elasticity has become poorer and poorer while being pressed repeatedly by the pressure-moved member for a long term and eventually resulted in the automatic swinging and resetting function mentioned above being lost practically.
In a pressure switch incorporating an ever-closed switch mechanism and being of such type that proper contact pressure of the corresponding contacts is assured by virtue of an elastic swinging and resetting force of the moving contact piece and that the corresponding contacts disengage in response to the contacting movement of pressure-moved member, there has been the possibility of failure to ensure adequate and sufficient contact making pressure because of substantial reduction in the self-retaining elasticity of said moving contact piece.
On the other hand, in a pressure switch enclosing an ever-open switch mechanism and being of such type that the moving contact piece swings to engage the corresponding fixed contact in response to the contacting travel of the pressure-moved member and that the moving contact piece swings to reset automatically with the self-retaining elasticity thereof to disengage the corresponding fixed contact in response to the returning travel of the pressure-moved member, the pressure switch has included the possibility that the moving contact piece fails to reset any more automatically as a result of the self-retaining elasticity thereof having nearly been lost and is left in touch with the corresponding fixed contacts. Problems can also arise where the moving contact happens to disengage the corresponding fixed contact at the moment of being subjected to vibration and/or shock, resulting in the switch no longer working normally. There is also another possibility that the moving contact piece may be bent or deformed by the overtravel of the pressure-moved member and result in the function provided as a pressure switch being spoiled.